I am trying to write a obj file with vertices. I am computing the vertex normals in my code and writing to this file as well. When I try to render this file in Meshlab it reads the vertices correctly, but when I go to 'Render->Show vertex normals', it is not showing the normals that I computed. Rather MeshLab computes its own normals and shows them.

I am not sure how I can visualize the normals that I computed/wrote to file. I want to apply Meshlab shader later based on my computed normals.

This is just one square. Now if I change the normal values in this file, it still shows its own vertex normals when I select 'Render->Show vertex normals'.
How can I have my own normals and apply shader that works on my computed normals?? Please help.